Leak-testing internal seals in pipe joints

ABSTRACT

The leak-testing of thread-connected, multiple-seal pipe joints is improved by connecting them to a limited extent that engages at least one internal seal without engaging the outermost seal, increasing the external fluid pressure to an amount significantly greater than the internal pressure, and detecting any resultant inflow of fluid.

I Unlted States Patent 11 1 3,653,254 Simon [4 1 Apr. 4, 1972 54]LEAK-TESTING INTERNAL SEALS 1N 2,695,632 11/1954 Brock ..73/46 x PIPEJOINTS I 3,371,521 3/1968 Hauk ..73/46 [72] Inventor: 22:12:12 A. Simon,Calgary, Alberta, Pfimay Examiner wuis R. Prince AssistantExaminer-William A. Henry, 11 1 Assisnw Shell Oil p y. New York,Attorney-Harold L. Denkler and Theodore E. Bieber [22] Filed: Oct. 16,1970 [57] ABSTRACT [211 App]. No.: 81,304

The leak-testing of thread-connected, multiple-seal pipe joints isimproved by connecting them to a limited extent that enil "73/33,! gasesat least one internal seal without engaging the outermost 5sF1616$65611................Q/E/ZEjE/fiiifis1;138/90; increasing the memefluid Pressure to 285/96 nificantly greater than the internal pressure,and detecting any resultant inflow of fluid.

[56] References Cited 4 C 2 Drawing Figures UNITED STATES PATENTSPATENTED R 4 I972 SHEET 1 [IF 2 Theodore A. Simon INVENTOR PATENTEDAPR 4m2 3. 653,254

sum 2 of 2 /N/T/AL MAKE- UP 6 M ,6 JO/NT B n JOINT c T;

75000 R A JO/NT O 1 SUBSEOUENT MAKE-UP G JO/NTA PREVIOUSLY OvERTOROUEOAND A PRESSURE TESTEO Q JO/NT A SUBSEOUENT A TESTS AFTER LEAK A AT FULLTORQUE Er I I Q JO/NTA W/TH 0.070

SH/M /N EXTERNAL SHOULDER L JOINT c AFTER 1500 FT LB TO OUE A JOINT DWITH HOLE IN OUTS/DE 14 INTERNAL SEAL BOX A JOINT D DAMAGED 14 SEAL WITHF/LE cORNER Theodore A. Simon INVENTOR LEAK-TESTING INTERNAL SEALS INPIPE JOINTS BACKGROUND OF THE INVENTION The invention relates toleak-testing the joints in pipe strings, such as tubing or casingstrings of the types used in the highest pressured wells, plants,refineries, etc. Such pipe joints are generally thread-connected,multiple-sealing joints, having at least one internal and one externalset of sealing shoulders. The pipe joints commonly used in high pressurewells are typified by the Hydril CS and PH tubing joints and highpressure casing joints.

In previously developed leak testing processes, such pipe joints aretested by connecting them substantially completely and applying anexternal or internal pressurization that is at least substantially equalto the full-rated pressure resistance of the joint. As indicated in USPat. No. 3,371,521, improved equipment and techniques are now availablefor applying such leak testing pressures externally at the site of a uselocation such as a well, plant, refinery, or the like, in which a pipestring is being installed.

SUMMARY OF THE INVENTION An internal seal in a thread-connected,multiple-seal pipe joint is leak-tested by connecting the joint to alimited extent at which at least one internal seal is engaged withoutengaging the external seal, increasing the external fluid pressure to avalue significantly greater than the internal pressure, and detectingany resultant inflow of fluid.

In a preferred embodiment, both the thread-connecting torque and thetest fluid pressurization are relatively small fractions of the amountscorresponding to the complete thread connection and full pressureresistance rating. The use of such reduced torque and pressures, in theabove manner, provides a testing of the internal seal that is actuallymore severe than a conventional type of internal testing that uses thefull connecting torque and the maximum fluid pressurization. The presentprocess, of externally pressurizing the fluid around a pipe jointconnected to an extent that engages only an internal seal, applies thefluid pressure so that it tends to disengage the internal seal and tocause leakage at rates that increase with increases in the testpressure. In contrast, a test using internal fluid pressurization tendsto apply the fluid pressure so that it may either seal or disengage theinternal seal depending upon connection configuration and may allow noleakage in response to increasing pressurization (until the joint wallsare ruptured). Because of this, the present process may be moredefinitive, with respect to the effectiveness of the internal seal, aswell as cheaper than conventional tests. The conventional tests use moreextensive torquing and pressurization and thus require greater operatingtime and expense.

The present internal seal testing with external test pressure at lowtorque is possible because of the relationship between make-up torqueand external leak pressure in multiple seal connections. In a torquerange such that only the internal seal is engaged (for example, up toone-third full recommended torque with respect to the Hydril CS and PHjoints), the external leak pressure is proportional to torque. At hightorque this relationship changes and is no longer representative ofinternal seal effectiveness. Since there is a design leak pressure (Le,a pressure that induces leakage when the sealing surfaces are undamaged)for a specific connection at a specific low torque, a leak observed at alower pressure indicates internal seal malfunction. Such defects asout-of-round pipe, internal lip or seal damage, foreign matter inthreads causing premature torque levels, external seal damage causingpremature shouldering, and improper machining tolerances, or the like,can result in a recognizable seal malfunction.

DESCRIPTION OF THE DRAWING FIG. 1 is a cross sectional view of thethreads and sealing elements of a I-lydril CS" pipe joint.

FIG. 2 is a plot of amounts of external fluid pressurization sufficientto cause leakage versus the torque applied in connecting the threads ofa tool joint.

DESCRIPTION OF THE INVENTION In making up a thread-connected,multiple-seal pipe joint, such as the Hydril CS joint of the type shownin FIG. 1, the first sealing occurs at the internal (14) seal ll. As thethreadconnecting torqueis increased, the external (60) seal 2 and theintermediate shoulder seal 3 are subsequently engaged.

FIG. 2 is a plot of the results of a series of tests on Hydril CS"tubing string joints (A, B, C and D) for 2 inch tubing. The data pointsfor the individual tests (described on the figure) are distinguished bysquares, circles, etc. In the plot, the ordinate is the external fluidpressure, in pounds per square inch, which was required to cause leakageinto the tool joint interior (at substantially atmospheric pressure) andthe abscissa is the amount of thread-connecting torque, in foot pounds,which was applied in connecting the joints. The zero point on theabscissa represents a hand tight make-up torque that allowed theexternal shoulder, at external seal 3 to remain off its seal by 0.011inch. Curve 6 shows the pressures required to cause leakage through newand undamaged pipe joints. Curve 7 shows the results with previouslyused, but undamaged, joints and curves 8 and 9 show the relatively lowpressures which are required to cause leakage through joints that weresubjected to the indicated types of actual or synthesized type ofdamage.

It will be apparent to those skilled in the art that where the internalseal is sound, the joint is likely to be sound. The tests of the presenttype can advantageously be conducted by applying only a fraction (forexample, 10 percent) of the full make-up torque and applying only afraction (for example, 30 percent) of the rated external pressure. If noleakage results, the internal seal can be assumed to be sound, and thepipe joint can be made up and used without further testing.

Ninety-one joints of 2 inch, 7.9 lb/ft, N- Hydril PH6-CB tubing werefield tested with the Gator Hawk external hydrostatic tester(substantially as described in US. Pat. No. 3,371,521) using relativelylow make-up torques and reduced pressures. The connections were testedwith a 0.002 inch gap (determined by feeler gauge) in the 60 externalseal to assure that the internal 14 primary seal was being tested.Make-up torque required to achieve this gap was 200 to 300 ft. lb.,while required make-up torque for this type of tubing is 3 ,000 ft. lb.

A two-step procedure was used for the tests. Eighty-two of the jointswere tested first to 5,500 p.s.i. at 200 to 300 ft. lb. torque with0.002 inch gap in the external 30 seal. If there was no leak, the jointswere then made up to full torque, 3,000 ft. lb., and tested to full testpressure, 9,000 p.s.i. One bad joint, caused by a mashed-in shoulder onthe 30 external seal on the pin, was detected in this group at 5,500p.s.i. The defect would not let the 14 internal seal preload enough tohold pressure. The last nine joints were tested first to 9,000 p.s.i. at200 to 300 ft. lb. torque with 0.002 inch gap in the external 30 seal.The joints were then made up to full torque, 3,000 ft. lb., and againtested to 9,000 p.s.i. No leaks were detected in this last group.

The present testing process can be applied to substantially anythread-connected, multiple-seal pipe joint. In general, the making-up ofthe pipe joint connecting threads and the application of the externalfluid pressurization can employ substantially any techniques andequipment adapted to cause one or more of the internal seals to beengaged without engaging the external seal and applying a fluid pressuredifferential that is significant but is less than the collapsingpressure of the tool joint. Such tests are preferably applied at thesite of a well in which an assembled pipe string is being installed.

The present invention can advantageously be used as a process fortesting pipe connections at the manufacturing plant for quality controlor for assembling and installing a pipe string in a well borehole, orthe like. The process comprises assembling a pipe string from sectionsjoined by thread-connected, multiple-seal pipe joints, connecting eachpipe joint to a limited extent at which at least one internal seal isengaged without engaging the external seal, increasing the externalfluid pressure to a selected value significantly higher than theinternal pressure, detecting any resultant inflow of fluid, completingthe connecting and installing of the pipe string with respect to eachpipe joint through which no leakage is induced, and disconnecting andcorrecting or replacing each pipe joint through which leakage isinduced.

What is claimed is 1. A process for leak testing a thread-connected,multipleseal pipe joint comprising:

connecting the joint to a limited extent that engages at least one innerseal without engaging the external seal; increasing the external fluidpressure to selected pressure significantly greater than the internalpressure; and detecting any resultant inflow of the pressurized externalfluid.

2. The process of claim 1 in which the amounts of torque, applied inconnecting the threads of the pipe joint, and external fluidpressurization are significantly less than those corresponding to fulltool joint connection torque and full rated pressure resistance of thetool joint.

3. The process of claim 1 in which the pipe joint connecting and testingis conducted at a use location on pipe joints which are being qualitycontrol tested in a pipe string.

4. A process for installing a pipe string in a borehole of a wellcomprising:

assembling a pipe string from sections joined by thread-connected,multiple-seal pipe joints;

partially connecting at least one pipe joint to a limited extent thatengages at least one inner seal without engaging the external seal;

increasing the external fluid pressure to a specific pressuresignificantly greater than the internal pressure within said partiallyconnected pipe joint;

detecting any resultant inflow of said pressurized external completingthe connecting and running into the borehole of pipe joints throughwhich no fluid inflow is induced; and disconnecting and correcting orreplacing pipe joints through which fluid inflow is induced.

m u m 2 w Notice of Adverse Decision in Interference In Interference No.98,115 involving Patent No. 3,653,254, T. A. Simon, LEAK-TESTINGINTERNAL SEALS IN PIPE JOINTS, final judgment adverse to the patenteewas rendered Feb. 28, 1974, as to claims 1, 2, and 3.

[Oficz'al Gazette M ay 21, 1.974.]

1. A process for leak testing a thread-connected, multiple-seal pipejoint comprising: connecting the joint to a limited extent that engagesat least one inner seal without engaging the external seal; increasingthe external fluid pressure to selected pressure significantly greaterthan the internal pressure; and detecting any resultant inflow of thepressurized external fluid.
 2. The process of claim 1 in which theamounts of torque, applied in connecting the threads of the pipe joint,and external fluid pressurization are significantly less than thosecorresponding to full tool joint connection torque and full ratedpressure resistance of the tool joint.
 3. The process of claim 1 inwhich the pipe joint connecting and testing is conducted at a uselocation on pipe joints which are being quality control tested in a pipestring.
 4. A process for installing a pipe string in a borehole of awell comprising: assembling a pipe string from sections joined bythread-connected, multiple-seal pipe joints; partially connecting atleast one pipe joint to a limited extent that engages at least one innerseal without engaging the external seal; increasing the external fluidpressure to a specific pressure significantly greater than the internalpressure within said partially connected pipe joint; detecting anyresultant inflow of said pressurized external fluid; completing theconnecting and running into the borehole of pipe joints through which nofluid inflow is induced; and disconnecting and correcting or replacingpipe joints through which fluid inflow is induced.